Low-cost realization of ISM band pass filters using integrated combline structures

Low-cost realization of ISM band pass filters using substrate-integrated combline structures has been demonstrated. For the low-cost realization and mass-production, efforts have been concentrated into realizing the combline filter structure as a integrated conductor layer of FR4/epoxy based multi-layer substrates which are widely used as multilayer printed circuit boards (PCB) instead of ceramic. By loading capacitive loads to each side of the combline strips, more reduction of the overall feature size has been achieved. Reasonable stopband and passband characteristics have been achieved. This filter can be used as a RF band pass filter for the wireless network devices of the 2.4 GHz ISM band such as Bluetooth and wireless LAN.